Base Station Calibration

1. A method of calibrating a base station comprising a plurality of antennas, the method comprising: receiving first correction information from a system module, the correction information determined from a first calibration of the base station; receiving at a radio frequency module signals received from at least one antenna of the base station; and determining second correction information on the basis of the received signals and the first correction information, wherein the received signals from the at least one antenna is a training sequence comprising signal distortions.

2. The method of claim 1 , wherein the method comprises: receiving a training sequence from the system module; and sending the training sequence to the at least one antenna of the base station.

3. The method of claim 1 , wherein receiving the first correction information comprises receiving correction information for correcting signal distortions or a training sequence modified on the basis of the correction information.

4. The method of claim 1 , wherein the first correction information is an error vector for correcting a fixed error and the second correction information is an error vector for correction a variable error.

5. The method of claim 1 , wherein the first correction information is determined during start up of the base station and the second correction information is determine after start up of the base station.

6. The method of claim 1 , wherein the method comprises measuring the characteristics of the received signals in response to the training sequence; and the determining the second correction information comprises estimating the error distortion of the signals on the basis of the measurements.

7. The method of claim 1 , wherein the training sequence is a start-up training sequence, a runtime training sequence, or both.

8. The method of claim 7 , wherein the method comprises measuring, at at least one of the system module or the radio frequency module, the characteristics of the received signals in response to the start-up training sequence; estimating, at at least one of the system module or the radio frequency module, the error distortion of the signals on the basis of the measurements.

9. The method of claim 8 , wherein the method comprises determining the first correction information on the basis of the estimated error distortion.

10. The method of claim 1 , wherein the method comprises: compensating signals received / transmitted from the base station, the signals being distorted by characteristics of at least one of the plurality of antennas, on the basis of the second correction information, on the basis of the first correction information, or on the basis of both the second correction information and the first correction information.

11. The method of claim 10 , wherein the compensating of the signals on the basis of the second correction information, on the basis of the first correction information, or on the basis of both the second correction information and the first correction information is carried out at at least one of the radio frequency module and the system module.

12. The method of claim 1 , wherein the method comprises: repeating receiving the signals from the at least one antenna and determining the second correction information.

13. The method of claim 1 , wherein the method comprises receiving first correction information for a first number of subbands and determining second correction information for a second number of subbands and the first number of subbands is greater than the second number of subbands.

14. The method of claim 13 , wherein the bandwidth of at least one suband of the first number of subbands is smaller that the bandwidth of at least one subband of the second number of subbands.

15. 1 The method of claim 1 , the determining comprises determining on or more of amplitude errors, phase errors or latency errors of signals.

16. A computer program product embodied on a non-transitory computer-readable medium in, which a computer program is stored that, when the program is run on a computer, is configured to provide instructions to control or carry out: receiving first correction information from a system module, the correction information determined from a first calibration of the base station; receiving a training sequence from the system module; sending the training sequence to the at least one antenna of the base station; receiving at a radio frequency module signals received from at least one antenna of the base station; and determining second correction information on the basis of the received signals and the first correction information.

17. The computer program product of claim 16 , wherein the received signals from the at least one antenna is a training sequence comprising signal distortions.

18. The computer program product of claim 16 , wherein the first correction information is determined during start up of the base station and the second correction information is determine after start up of the base station.

19. An apparatus comprising: a processor; memory including computer program code; the memory and the computer program code configured to, with the processor, cause the apparatus to perform at least the following: receive first correction information from a system module, the correction information determined from a first calibration of the base station; receive at a radio frequency module signals received from at least one antenna of the base station; and determine second correction information on the basis of the received signals and the first correction information, wherein the first correction information is determined during start up of the base station and the second correction information is determine after start up of the base station.

20. The apparatus of claim 19 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to perform at least the following: receive a training sequence from the system module; and send the training sequence to the at least one antenna of the base station.

21. The apparatus of claim 19 , wherein receiving the first correction information comprises receiving correction information for correcting signal distortions or a training sequence modified on the basis of the correction information.

22. The apparatus of claim 19 , wherein the first correction information is an error vector for correcting a fixed error and the second correction information is an error vector for correction a variable error.

23. The apparatus of claim 19 , wherein the received signals from the at least one antenna is a training sequence comprising signal distortions.

24. The apparatus of claim 19 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to perform at least the following: measure the characteristics of the received signals in response to the training sequence.

25. The apparatus of claim 24 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to perform at least the following: determine the second correction information comprises estimating the error distortion of the signals on the basis of the measurements.

26. The apparatus of claim 19 , wherein the training sequence is a start-up training sequence, a runtime training sequence, or both.